Subunits of the Small‐Intestinal Sucrase · Isomaltase Complex and Separation of Its Enzymatically Active Isomaltase Moiety

The size and number of subunits of the sucrase · isomaltase complex (mol. wt approximately 220000) from rabbit small intestine were determined by dodecylsulfate‐polyacrylamide gel electrophoresis, gel filtration and fingerprint analysis of tryptic hydrolysates. It was found that two subunits of similar size (estimated mol. wt 110000 to 120000 each) build up the sucrase · isomaltase complex, the one carrying sucrase, the other isomaltase activity. The isolation of the active isomaltase moiety, along with small amounts of active sucrase as a byproduct, has been achieved. Amino acid and carbohydrate analysis of the two subunits are reported.